Embedding a sphere within a hemisphere
Boolean difference modifier
A boolean difference modifier will do this for us. Simply need the two spheres and a &quot;chopping block&quot; object.

Two UV spheres, smaller in larger.  Use the cube as a difference boolean modifier target to cut away from the outer.
The cube is displayed as a wireframe, and can be hidden from render (and or viewport)
Could also use the inner to &quot;core&quot; out the slot.

Can transform, or change the chopping &quot;cube&quot; to for example a spin modifier created cylinder to animate a reveal.
How to use a mesh to reveal an object
Re a blurry material see
material issue - how to make blurry/emissive material?
Related
Create a sphere with multiple layers and a chunk cut out showing them